Analysis on signals, such as communication data, transmitted via a communication line has been made possible by, for example, a communication-status analysis system disclosed in Patent Literature 1, an air-conditioning communication data collection device disclosed in Patent Literature 2, and a network monitoring device disclosed in Patent Literature 3.
The communication-status analysis system disclosed in Patent Literature 1 receives communication data (signal) from communication network connected with a plurality of controllers including communication circuits, and stores communication data. The communication-status analysis system selects communication data of a specific controller (for example, a controller assumed as defective) from the stored communication data. Next, the communication-status analysis system re-transmits communication data transmitted from the controller other than the selected and specific controller to the selected and specific controller. This re-transmission enables a user to analyze a communication status (reception analysis for communication data) for the specific controller.
The air-conditioning communication data collection device disclosed in Patent Literature 2 stores, when detecting an anomaly in communication packets transmitted via a communication line, signal waveform data at the time points before and after the anomaly is detected. The air-conditioning communication data collection device then analyzes the stored signal waveform data. This makes it possible for the user to analyze any anomaly occurred in the signal waveform data (signals).
The network monitoring device disclosed in Patent Literature 3 stores transmission data that is transmitted via network (communication line). Such stored transmission data enables the user to analyze the transmission status of transmission data and the transmission details of the transmission data. The stored transmission data is constituted by a value of current and that of voltage (value of current flowing through power cable and value of voltage applied across the power cable) that are collected from network.